More detailed explanations for these commits.
1) FRED: Validate user-provided values passed to Random::next()
When rand and rand-multiple sexps or the rand32 scripting functions are used, previously they would accept nonsense inputs like 0 or negative numbers. This patch shows a warning if this is tried.
2) FSO: fix ai_aims_from_center flag
Fixes this flag so that it actually works. Previously, it would only help ai aim from the center point of their fighter when using gun convergence.
3) FSO: remove glowpoint 'depth'
This gets rid of an odd portion of the glowpoint calculation that would separate the glowpoint from the model from certain distances and angles.